I need ideas for a Mantis starter Pokémon, like for an entire line, got anything
Without specifying the type you were specifically looking for or giving me any other information I can’t really give you much in the way of specific help; your best best (really, in general) if you have absolutely nothing to go on is going to be to google mantises and read about them until something interesting strikes you. As a starting point, though, there are always those forelegs. Obviously scyther has the big blade thing down already, but since in real mantises they’re actually used for grabbing and holding rather than slashing, you could use that angle instead.
A more interesting option would be to take a supernatural bent: they’re often called “praying” mantises, and mantises were/are often associated with meditation and with seeing the future. There’s material for a psychic-type in there. You could also base it on mantis-inspired martial arts styles and get a fighting-type out of it.
And of course, if you’re looking for a grass starter specifically, there are the leaf-mimicking, jeweled leaf and orchid mantises. The new pokémon fomantis and lurantis are already orchid mantises, but they’re such striking and colorful insects that I’m sure you could get a sufficiently different design out of them.